The invention relates generally to ion laser structures, and more particularly to water-cooled ion lasers including an electromagnet.
Ion laser structures are generally described in Miller, et al., U.S. Pat. No. 4,715,039, issued Dec. 22, 1987, which is hereby incorporated by reference into this specification in full. The structure typically comprises a plasma tube and an optical resonator. The plasma tube contains the gain medium, a plasma created by running a discharge between an anode and cathode mounted at opposite ends of the tube. The optical resonator supports a pair of spaced, opposed, aligned mirrors, positioned at opposing ends of the gain medium to produce lasing action. The plasma tube is disposed within the resonator by complex mounting arrangements.
In operation, a laser, such as an ion laser, generates considerable heat, which must be removed, at least in applications where stability of laser output is critical. The heat can cause thermal expansion of the resonator structure and can adversely affect the mirror alignment and thus the laser output. Water cooling of the laser is frequently utilized to minimize this problem.
By applying a magnetic field to the plasma in an ion laser tube, higher gain and efficiency are obtained. Most water cooled ion lasers include an electromagnet disposed around the plasma tube. Since the electromagnet also generates heat, it too can be water cooled.
To be most effective, the water cooling of the laser resonator must be uniform. A temperature difference between the top and bottom of the resonator may be sufficient to bend the resonator significantly, misaligning the mirrors and changing the laser output, even preventing lasing. This problem can be reduced by providing a thermal short between the top and bottom of the resonator.
Miller, et al., provided an advance in the art by utilizing a monolithic structure in which the plasma tube, surrounded by an electromagnet, is mounted in a concentrically spaced relationship within the laser resonator tube in a single unitary water cooled structure. Inner and outer flow channels are respectively defined between the plasma tube and electromagnet, and the electromagnet and resonator tube. With this integrated assembly, the complexity is minimized while the efficiency is greatly improved.
The invention of Miller, et al., although an important advance in the art of ion laser construction, can still be improved from the standpoint of the manufacturer and the user. For example, it is sometimes difficult to service the ends of the resonator tube, in which the mirrors forming the optical resonator are disposed, because of constrained accessibility within the wholly-contained end cavities. Moreover, hot air may become trapped in these end cavities such that the heat transfer into the coolant adjacent thereto is less efficient than in the central portion of the resonator containing the electromagnet. Finally, the longer the resonator tube, the more difficult it is to meet manufacturing tolerances required by ion laser technology. Thus, there exists a need in the art for further improvements in ion laser resonator design to address these problems.
Accordingly, it is an object of the present invention to provide a resonator design for water-cooled ion gas lasers in which the advantages of an integrated resonator design are retained, but performance is enhanced by substantially eliminating trapped air and end-cavity heat exchange problems.
It is a further object of the invention to reduce manufacturing tolerance difficulties for resonator tubes for water-cooled ion gas lasers, and accordingly to decrease manufacturing cost.
It is another object of the invention to improve serviceability and ease of assembly of water-cooled ion gas lasers.
It is still a further object of the invention to increase manufacturing flexibility and reduce costs by providing a relatively modular design, in which a fewer number of resonator tubes can be used with a greater number of laser designs utilizing varying optical lengths.